Heretofore, there have been employed dynamic dampers as vibration reducing apparatuses (vibration attenuators), as disclosed in Japanese Laid-Open Utility Model Publication No. 05-026745 and Japanese Laid-Open Patent Publication No. 2001-227582.
Japanese Laid-Open Utility Model Publication No. 05-026745 reveals a vehicular auxiliary supporting apparatus, wherein an engine auxiliary such as an alternator or the like is disposed in a position aligned with a vibrational antinode of a subframe. In operation, the engine auxiliary oscillates in order to cancel out vibrations of the subframe, and hence the engine auxiliary acts as a dynamic damper.
Japanese Laid-Open Patent Publication No. 2001-227582 discloses a dynamic damper including a mass mounted on a rectangular arm of a subframe by an elastic rubber body (this assembly will hereinafter be referred to as an “elastic mass and rubber assembly”). The elastic mass and rubber assembly is set to a resonant frequency that matches the resonant frequency of the subframe. At times when the engine is in operation, when engine vibrations are applied to the subframe, thereby causing the subframe to resonate, the elastic mass and rubber assembly resonates in order to suppress resonant vibrations of the subframe.
Japanese Laid-Open Patent Publication No. 05-069853 discloses a vehicle-mounted active vibration reducing apparatus for an elongate subframe, opposite ends of which are coupled to a vehicle body by respective dampers. The vehicle-mounted active vibration reducing apparatus includes a piezo actuator connected in parallel to the damper at one end of the elongate subframe. In operation, the piezo actuator is operated in opposite phase with vibrations that occur at the other end of the subframe, thereby reducing vibrations of the subframe.